Theorem 3.10 (see [1]} or [2]}) 
With respect to the multiplication defined by the Stong projection \(\pi _0\) , the ring \(^W\)  is polynomial on generators in every positive even degree
except 4:
\(^W \cong \mathbb {Z}[x_1, x_k \colon k \geqslant 3], \quad x_1=[\mathbb {C}P^1], \quad x_k \in _{2k}^W.\) 
